Treatment of liquids with ballasted flocculation

Abstract

In the typical embodiments disclosed in the specification, a ballasted flocculation liquid treatment arrangement includes a mixing chamber in which liquid to be treated, flocculating agents and granular material are mixed. The mixture is supplied to the bottom of a flocculating chamber adjacent to the mixing chamber through an opening in a common wall between the chambers and is maintained in suspension in the flocculating chamber by turbulence generated by a rotating blade array. Ballasted flocs are transferred from the flocculation chamber to an adjacent sludge tank through a first opening in a common wall between them and liquid which contains lighter flocs is returned to the flocculation chamber through a second opening in the common wall. Liquid from the flocculation chamber passes upwardly through a turbulence control arrangement where flocs and particulates are substantially removed and into a clarification chamber where clarified liquid is passed over a weir to an outlet. Sludge and granular material from the bottom of the sludge tank are conveyed by an airlift to a cleaning device above the mixing chamber where the granular material is cleaned and returned to the mixing chamber while sludge is carried away through a disposal outlet.

I claim:  
     
       1. A ballasted flocculation liquid treatment arrangement comprising: 
       a mixing chamber to receive and mix liquid, granular material and a flocculating agent;  
       a flocculation chamber receiving a mixture of liquid, granular material and flocculating agent from the mixing chamber and providing sufficient turbulence of the mixture to maintain the constituents in suspension and promote flocculation;  
       a sludge tank adjacent to and communicating with the flocculation chamber for receiving ballasted flocs from the flocculation chamber;  
       a clarification chamber disposed above the flocculation chamber to receive liquid from the flocculation chamber; and  
       a turbulence control arrangement extending horizontally between the flocculation chamber and the clarification chamber for separating liquid from flocs and particulates and permitting liquid to pass upwardly from the flocculation chamber to the clarification chamber without causing substantial turbulence in the clarification chamber while permitting particulates to fall from the clarification chamber into the flocculation chamber.  
     
     
       2. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement comprises a plurality of layers of horizontal bars with the bars of adjacent layers extending at an angle to each other. 
     
     
       3. A ballasted flocculation liquid treatment arrangement according to  claim 2  wherein bars in each layer are spaced by about one quarter inch to one and one-half inches. 
     
     
       4. A ballasted flocculation liquid treatment arrangement according to  claim 2  wherein the bars in each layer are spaced by about one-half inch to one inch. 
     
     
       5. A ballasted flocculation liquid treatment arrangement according to  claim 2  wherein the layers are spaced by about one inch to about three inches. 
     
     
       6. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement comprises at least two horizontal arrays of baffles inclined in opposite directions from the vertical. 
     
     
       7. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement comprises a shelf extending inwardly from vertical walls defining the flocculation chamber, the shelf being inclined at an angle of about 30° to about 60° from the horizontal and projecting inwardly from each wall a horizontal distance of about 10% to about 20% of the width of the flocculation chamber. 
     
     
       8. A ballasted flocculation liquid treatment arrangement according to  claim 7  wherein the shelf extends inwardly at an angle of about 45° from the horizontal. 
     
     
       9. A ballasted flocculation liquid treatment arrangement according to  claim 7  wherein the shelf extends inwardly from each walls of the flocculation chamber a horizontal distance of about 15% of the width of the flocculation chamber. 
     
     
       10. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement comprises a honeycomb array of vertically oriented cells covered by a top plate having orifices permitting quiescent flow of liquid upwardly from the flocculation chamber. 
     
     
       11. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement comprises an array of inclined plates covered by a top plate having orifices permitting quiescent flow of liquid from the flocculation chamber to the clarification chamber. 
     
     
       12. A ballasted flocculation liquid treatment arrangement according to  claim 11  including an effluent trough surrounding the top plate. 
     
     
       13. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement includes a porous membrane having a porosity great enough to permit quiescent flow of liquid upwardly from the flocculation chamber. 
     
     
       14. A ballasted flocculation liquid treatment arrangement according to  claim 1  wherein the turbulence control arrangement comprises a vertically spaced series of horizontal screens having openings of a size sufficient to inhibit turbulence in a liquid passing upwardly from the flocculation chamber. 
     
     
       15. A ballasted flocculation liquid treatment arrangement according to  claim 14  wherein the flocculation chamber includes at least one rotating blade set for producing turbulence to maintain the granular material and flocs in suspension. 
     
     
       16. A ballasted flocculation liquid treatment arrangement according to  claim 15  wherein the flocculation chamber includes at least one horizontal partition providing partial separation between adjacent vertically spaced compartments in the flocculation chamber and the turbulence producing arrangement includes at least one rotating blade set in each compartment. 
     
     
       17. A ballasted flocculation liquid treatment arrangement according to  claim 15  wherein the rotating blade set produces a toroidal liquid flow pattern moving upwardly along the walls of the chamber and downwardly near the center of the chamber. 
     
     
       18. A ballasted flocculation liquid treatment arrangement according to  claim 1  including a cleaning device for separating granular material from sludge and returning the granular material to the mixing chamber for mixing with influent liquid and flocculating agent and having an outlet for sludge removed from the granular material. 
     
     
       19. A ballasted flocculation liquid treatment arrangement according to  claim 18  including a conveyor for conveying granular material and sludge from the bottom of the sludge tank to the cleaning device. 
     
     
       20. A ballasted flocculation liquid treatment arrangement according to  claim 19  wherein the conveyor is an airlift. 
     
     
       21. A ballasted flocculation liquid treatment arrangement comprising: 
       a mixing tank for mixing granular material, liquid and a flocculating agent;  
       a flocculation chamber laterally adjacent to the mixing tank to receive a mixture therefrom through an opening in a common wall;  
       a clarification chamber above the flocculation chamber to receive liquid therefrom, a turbulence control arrangement extending horizontally between the flocculation chamber and the clarification chamber for eliminating turbulence in liquid passing from the flocculation chamber to the clarification chamber, while permitting particulates to fall from the clarification chamber into the flocculation chamber; and  
       a sludge tank laterally adjacent to the flocculation chamber to receive ballasted flocs through an opening in a common wall between the sludge tank and the flocculation chamber.  
     
     
       22. A ballasted flocculation liquid treatment arrangement according to  claim 21  wherein the sludge tank is laterally adjacent to the mixing tank and including a cleaning device above the mixing tank for cleaning recirculated granular material and depositing cleaned granular material into the mixing tank, and a conveyer for conveying sludge and granular material from the bottom of the sludge tank to the cleaning device. 
     
     
       23. A ballasted flocculation liquid treatment arrangement according to  claim 22  wherein the conveyor comprises an airlift.